In medical practice, when it is desired to introduce drugs or the like into the human system slowly and continuously, it has been common practice to use intravenous injection. This is accomplished by use of a hollow needle having a flexible tube leading to a bottle that contains the drug in solution. It has also been possible to introduce the drug through the skin by osmosis or infusion, as in the case of nitroglycerin, in cases where the amount of drug to be introduced is small and the infusion is to take place very slowly. However, both of these methods have shortcomings. The intravenous injection into the vein is uncomfortable and sometimes dangerous. Furthermore, an I.V. injection must be performed by a "skilled" medical professional. It certainly limits the activity of the patient. In the case of children, the pain of injecting the needle is a considerable problem. On the other hand, the infusion pad used with nitroglycerin and the like allows only a limited amount of fluid to enter the skin; furthermore, the release of drug from the reservoir contained in the pad is such that the rate of infusion takes place very strongly with a new pad, but, as time passes, the rate decreases because of the amount of drug in the reservoir has been reduced. Also, the conventional infusion pad (containing a reservoir of the medication) has a limited "shelf life" and is ineffective after a certain period. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a transdermal infusion device giving the combined advantages of intravenous introduction and the use of an infusion pad.
Another object of this invention is the provision of a transdermal infusion device which allows continuous introduction of a drug without the rate of infusion falling during the process.
A further object of the present invention is the provision of a device for the transdermal infusion of a drug, which device is simple in construction, which is inexpensive to manufacture, and which is capable of a long use with a minimum of care.
It is another object of the instant invention to provide a device for the introduction of a drug continuously into the human body without piercing the skin, wherein the rate of introduction is maintained at a constant level.
Another object of the invention is the provision of a drug-introduction device that can be placed by a person who is not a skilled medical professional.
A further object of the invention is a pad having an unlimited shelf life, since it is stored free of medication.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.